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slow and gradual but often interrupted movements。 The second related to the great masses of crystalline rocks which； underlying the muds； cover so great a part of the continent。 Darwin； almost as soon as he landed； was struck by the circumstance that the direction； as shown by his compass； of the prominent features of these great crystalline rock…massestheir cleavage； master…joints； foliation and pegmatite veinswas the same as the orientation described by Humboldt （whose works he had so carefully studied） on the west of the same great continent。
The first five chapters of the book on South America were devoted to formations of recent date and to the evidence collected on the east and west coasts of the continent in regard to those grand earth…movements； some of which could be shown to have been accompanied by earthquake…shocks。 The fossil bones； which had given him the first hint concerning the mutability of species； had by this time been studied and described by comparative anatomists； and Darwin was able to elaborate much more fully the important conclusion that the existing fauna of South America has a close analogy with that of the period immediately preceding our own。
The remaining three chapters of the book dealt with the metamorphic and plutonic rocks； and in them Darwin announced his important conclusions concerning the relations of cleavage and foliation； and on the close analogy of the latter structure with the banding found in rock…masses of igneous origin。 With respect to the first of these conclusions； he received the powerful support of Daniel Sharpe； who in the years 1852 and 1854 published two papers on the structure of the Scottish Highlands； supplying striking confirmation of the correctness of Darwin's views。 Although Darwin's and Sharpe's conclusions were contested by Murchison and other geologists； they are now universally accepted。 In his theory concerning the origin of foliation； Darwin had been to some extent anticipated by Scrope； but he supplied many facts and illustrations leading to the gradual acceptance of a doctrine which； when first enunciated； was treated with neglect； if not with contempt。
The whole of this volume on South American geology is crowded with the records of patient observations and suggestions of the greatest value； but； as Darwin himself saw； it was a book for the working geologist and 〃caviare to the general。〃 Its author； indeed； frequently expressed his sense of the 〃dryness〃 of the book； he even says 〃I long hesitated whether I would publish it or not；〃 and he wrote to Leonard Horner 〃I am astonished that you should have had the courage to go right through my book。〃 （〃M。L。〃 II。 page 221。）
Fortunately the second book； on which Darwin was engaged at this time； was of a very different character。 His 〃Journal〃； almost as he had written it on board ship； with facts and observations fresh in his mind； had been published in 1839 and attracted much attention。 In 1845； he says； 〃I took much pains in correcting a new edition；〃 and the work which was commenced in April； 1845； was not finished till August of that year。 The volume contains a history of the voyage with 〃a sketch of those observations in Natural History and Geology； which I think will possess some interest for the general reader。〃 It is not necessary to speak of the merits of this scientific classic。 It became a great favourite with the general public having passed through many editionsit was； moreover； translated into a number of different languages。 Darwin was much gratified by these evidences of popularity； and naively remarks in his 〃Autobiography〃； 〃The success of this my first literary child tickles my vanity more than that of any of my other books〃 （〃L。L。〃 I。 page 80。）and this was written after the 〃Origin of Species〃 had become famous！
In Darwin's letters there are many evidences that his labours during these ten years devoted to the working out of the geological results of the voyage often made many demands on his patience and indomitable courage。 Most geologists have experience of the contrast between the pleasures felt when wielding the hammer in the field； and the duller labour of plying the pen in the study。 But in Darwin's case； innumerable interruptions from sickness and other causes； and the oft…deferred hope of reaching the end of his task were not the only causes operating to make the work irksome。 The great project； which was destined to become the crowning achievement of his life； was now gradually assuming more definite shape； and absorbing more of his time and energies。
Nevertheless； during all this period； Darwin so far regarded his geological pursuits as his PROPER 〃work；〃 that attention to other matters was always spoken of by him as 〃indulging in idleness。〃 If at the end of this period the world had sustained the great misfortune of losing Darwin by death before the age of fortyand several times that event seemed only too probablehe might have been remembered only as a very able geologist of most advanced views； and a traveller who had written a scientific narrative of more than ordinary excellence！
The completion of the 〃Geology of the 'Beagle'〃 and the preparation of a revised narrative of the voyage mark the termination of that period of fifteen years of Darwin's life during which geological studies were his principal occupation。 Henceforth； though his interest in geological questions remained ever keen； biological problems engaged more and more of his attention to the partial exclusion of geology。
The eight years from October； 1846； to October； 1854； were mainly devoted to the preparation of his two important monographs on the recent and fossil Cirripedia。 Apart from the value of his description of the fossil forms； this work of Darwin's had an important influence on the progress of geological science。 Up to that time a practice had prevailed for the student of a particular geological formation to take up the description of the plant and animal remains in itoften without having anything more than a rudimentary knowledge of the living forms corresponding to them。 Darwin in his monograph gave a very admirable illustration of the enormous advantage to be gainedalike for biology and geologyby undertaking the study of the living and fossil forms of a natural group of organisms in connection with one another。 Of the advantage of these eight years of work to Darwin himself； in preparing for the great task lying before him； Huxley has expressed a very strong opinion indeed。 （〃L。L。〃 II。 pages 247…48。）
But during these eight years of 〃species work；〃 Darwin found opportunities for not a few excursions into the field of geology。 He occasionally attended the Geological Society； and； as we have already seen； read several papers there during this period。 His friend； Dr Hooker； then acting as botanist to the Geological Survey； was engaged in studying the Carboniferous flora； and many discussions on Palaezoic plants and on the origin of coal took place at this period。 On this last subject he felt the deepest interest and told Hooker； 〃I shall never rest easy in Down churchyard without the problem be solved by some one before I die。〃 （〃M。L。〃 I。 pages 63； 64。）
As at all times； conversations and letters with Lyell on every branch of geological science continued with unabated vigour； and in spite of the absorbing character of the work on the Cirripedes； time was found for all。 In 1849 his friend Herschel induced him to supply a chapter of forty pages on Geology to the Admiralty 〃Manual of Scientific Inquiry〃 which he was editing。 This is Darwin's single contribution to books of an 〃educational〃 kind。 It is remarkable for its clearness and simplicity and attention to minute details。 It may be read by the student of Darwin's life with much interest； for the directions he gives to an explorer are without doubt those which he； as a self…taught geologist； proved to be serviceable during his life on the 〃Beagle〃。
On the completion of the Cirripede volumes； in 1854； Darwin was able to grapple with the immense pile of MS。 notes which he had accumulated on the species question。 The first sketch of 35 pages （1842）； had been enlarged in 1844 into one of 230 pages （＇The first draft of the 〃Origin〃 is being prepared for Press by Mr Francis Darwin and will be published by the Cambridge University Press this year （1909）。 A。C。S。＇）； but in 1856 was commenced the work （never to be completed） which was designed on a scale three or four times more extensive than that on which the 〃Origin of Species〃 was in the end written。
In drawing up those two masterly chapters of the 〃Origin〃； 〃On the Imperfection of the Geological Record；〃 and 〃On the Geological Succession of Organic Beings〃； Darwin had need of all the experience and knowledge he had been gathering during thirty years； the first half of which had been almost wholly devoted to geological study。 The most enlightened geologists of the day found much that was new； and still more that was startling from the manner of its presentation； in these wonderful essays。 Of Darwin's own sense of the importance of the geological evidence in any presentation of his theory a striking proof will be found in a passage of the touching letter